Linea nigra
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Synopsis
Linea nigra is thought to be a consequence of increased production of melanin secondary to increased circulating levels of estrogen, progesterone, and melanocyte stimulating hormone (MSH) in pregnancy. Upregulation by human placenta lipids of tyrosinase has also been hypothesized to play a role. In 90% of pregnant individuals, hyperpigmentation of some type is seen, including darkening of the areolae, ephelides, scars, or melasma. Women with lighter skin phototypes develop hyperpigmentation less often than women with darker pigmentation. Linea nigra tends to appear around the second or third trimester. After birth, the line fades over time, but it may never disappear entirely.
In a population-based study of Nigerians, linea nigra was found to be present in both male and female patients. For males, incidence peaked at 40% in the 11- to 15-year-old age group, whereas in females, incidence was highest in the 16- to 30-year-old group, in which 85% were affected. Pregnant individuals were 60 times more likely than nonpregnant individuals to have linea nigra. In males, an increased incidence has been noted in patients with prostate cancer and benign prostatic hypertrophy. Its use as a screening tool for prostate cancer has been suggested, but it was not found to be a sensitive marker in one study.
Related topic: linea nigra in newborn
Codes
ICD10CM:L81.8 – Other specified disorders of pigmentation
O26.90 – Pregnancy related conditions, unspecified, unspecified trimester
SNOMEDCT:
90751002 – Linea nigra
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Diagnostic Pearls
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Differential Diagnosis & Pitfalls
- Café au lait macule – Generally not linear and vertically oriented.
- Postinflammatory hyperpigmentation – Patient would have a history of prior inflammation.
- Flagellate hyperpigmentation – Patient would have history of bleomycin exposure (drug-induced flagellate pigmentation) or shiitake mushroom ingestion (flagellate mushroom dermatitis).
- Melasma – Much more commonly presents on the face and upper body.
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Therapy
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References
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Last Reviewed:08/11/2020
Last Updated:08/12/2021
Last Updated:08/12/2021
Patient Information for Linea nigra
Overview
Linea nigra is a dark vertical line that appears on the belly during pregnancy. It can extend from the top of the belly to the pubic area, running through the center of the belly button, or the line can be shorter. Increased hormones present during pregnancy stimulate increased pigment production, causing this area to darken. After the baby is born, the line of linea nigra typically fades. Depending on your skin color, this may take up to a year after pregnancy.Who’s At Risk
Linea nigra tends to appear some time in the second trimester of pregnancy. It is more prominent in women of color. It is also present on women with light skin, though it is not as noticeable.Signs & Symptoms
The line of linea nigra is darker than the surrounding skin and approximately a centimeter in width. It can be quite dark or fairly light in color.Self-Care Guidelines
No treatment is needed. The line should slowly fade after the baby is born. However, sun exposure can cause it to become darker or take longer to go away, so use a sunblock (at least SPF 15) or keep your belly covered.When to Seek Medical Care
No medical care is needed to treat linea nigra. Continue to take your prenatal vitamins and otherwise follow routine prenatal care guidelines.Treatments
Your doctor will continue routine prenatal care.References
Bolognia, Jean L., ed. Dermatology, p. 990. New York: Mosby, 2003.
Wolff, Klaus, ed. Fitzpatrick's Dermatology in General Medicine. 7th ed, pp. 635, 955. New York: McGraw-Hill, 2008.
Linea nigra